1. Field of the Invention
The present invention relates to a fixture for securing a temperature detection element and a method of securing the temperature detection element therewith. In particular, the present invention relates to a fixture securing a temperature detection element to windings (magnetic wire portion) wound around a stator core in a motor, a motor to which the fixture is provided, and a method for securing a temperature detection element in a motor.
2. Description of the Related Art
FIG. 9 schematically illustrates the internal configuration of a common motor. A common motor 1 comprises a rotor 3 which rotates around a central shaft 2, and a stator 4 which applies a magnetic rotational force to the rotor. On the inner peripheral surface of the stator 4, a plurality of protrusions 4a are formed equidistantly in the circumferential direction of the rotor 3. Copper wires (conductive wires) 5 are wound around the protrusions 4A, the copper wires being coated by an insulating layer (not shown). Further, FIG. 9 illustrates the motor 1 which generates rotational motion, however, a motor which generates linear motion, namely a linear motor is also well known. A stator of a linear motor uses a magnetic plate which extends in a straight line, on which a plurality of protrusions are formed equidistantly along the extending direction, and copper wires are wound around the protrusions.
Hereinafter, the portions formed from wires wound around the circumference of the protrusions will be referred to as windings. Further, the term stator core may be used to refer to the protrusions.
The windings of an electric motor, as described above, generate heat due to copper loss or iron loss, etc. When a high load is required of an electric motor, it is necessary to apply a large current through the windings, thus the windings rapidly generate heat. If the temperature of the windings exceeds a predetermined temperature, the insulating layer of the copper wire may melt or burn out. In such cases there is a risk of the copper exposed from the insulating layer contacting a nearby conductor and causing an electrical short. Accordingly, there is a need to secure a temperature detection element to the windings to thereby swiftly and accurately detect when the temperature exceeds the predetermined temperature of the windings in order to prevent such problems from occurring. As methods for securing a temperature detection element to a winding, the following conventional examples have been used.
FIGS. 10A and 10B illustrate the first conventional example of a method for securing a temperature detection element to a winding. FIG. 10A is a lateral view showing part of a stator of a linear motor, and FIG. 10B is a plan view of the stator shown in FIG. 10A.
According to the first conventional example, as shown in FIGS. 10A and 10B, a temperature sensitive part of a temperature detection element 9 is secured to the outer surface of a winding 7 provided around any stator core 6 by an adhesive 8.
FIG. 11 is a lateral view of the stator of the second conventional example.
According to the second conventional example, as shown in FIG. 11, a temperature sensitive part of a temperature detection element 9 is disposed on the outer surface of a winding 7. A string 10 is passed through a gap between the winding 7 and a stator core 6 and wound onto one side of the winding 7, thereby securing the temperature sensitive part of the temperature detection element 9 between the string 10 and the winding 7.
Furthermore, Japanese Patent Laid-Open No. 2003-92858 discloses another method for securing a temperature detection element onto windings.
In the method described in Japanese Patent Laid-Open No. 2003-92858, a guide provided with a cut-out portion formed to be open at one end thereof is inserted into a gap between a stator core and the coil end of the windings. The other end of the guide is the front end in the insertion direction and is provided with elastically deformable hooks. The guide is inserted into the gap by deforming the hooks, and when the other end of the guide is released from the gap, the hooks engage with the rim of the opening of the winding to thereby secure the guide thereto. Next, the temperature sensitive part of the temperature detection element is inserted into the cut-out portion through the opening of the one end of the guide and the temperature sensitive part is made to contact the inside surface of the windings. Further, the bottom of the cut-out portion in which the temperature sensitive part is to be housed is configured to be resilient, so that the temperature sensitive part of the temperature detection element can be strongly pressed against the inside surface of the winding.
However, in the first conventional example, the temperature detection element 9 may be accidentally displaced before the adhesive with which the temperature sensitive part of the temperature detection element 9 is adhered to the outer surface of the winding 7 completely hardens. Thus the temperature sensitive part of the temperature detection element may be secured to a position of the winding 7 different from a desired position for measuring the temperature, and the problem of not being able to obtain the expected accuracy of temperature detection may occur.
In the second conventional example, securing the temperature sensitive part of the temperature detection element 9 by the string wound onto the one side of the winding 7 is not simple, requiring a large number of man-hours. Further, a certain amount of skill is required in order to accurately secure the temperature sensitive part of the temperature detection element 9 to the desired position for measuring the temperature of the winding 7.
Further, in securing methods utilizing an adhesive as in the first conventional example, it is difficult to correct the position of the temperature detection element after the adhesive has completely hardened. Whereas, in securing methods utilizing a string as in the second conventional example; it is possible to correct the position of the temperature detection element. However, much time and effort is required for the correction as the work requires unraveling the string, adjusting the position of the temperature detection element and retying the string.
Further, in the other conventional example, as described in Japanese Patent Laid-Open No. 2003-92858, as the temperature sensitive part of the temperature detection element contacts the inside surface of the winding, it is necessary to design the shape of the outer surfaces of the guide and the temperature sensitive part to fit the shape, for example the curvature, of the inner surface of the winding. Namely, a method for closely attaching each of the outer surfaces of the guide and the temperature sensitive part to the inner surface of the winding is employed. Thus it is not easy to remove the guide from the gap between the stator core and the coil end of the windings after the guide and the temperature detection element have been inserted into the gap between the stator core and the coil end.
Moreover, Japanese Patent Laid-Open No. 2003-92858 describes that the hooks are provided on the other end of the guide which is the front end in the insertion direction, and engage the rim of the opening of the winding when released from the gap. Thus it is necessary to deform the hooks when removing the guide from the gap.
Therefore, in the method described in Japanese Patent Laid-Open No. 2003-92858, it is not easy to secure or adjust the position of the temperature sensitive part of the temperature detection element with respect to the inner surface of the winding.